Epilepsy is a disorder of the brain characterized by recurring seizures, in which there are uncontrolled electrical discharges of brain cells. Epilepsy may arise from a very small area of damaged brain tissue, or from the entire brain. There may be no apparent brain damage, or damage may be limited to an area so small it cannot be detected. Therefore, in nearly one-half the cases, the cause of epilepsy is unknown.
There are several types of seizures associated with epilepsy, the most common of which are generalized tonic-clonic (grand mal), absence (petit mal), complex partial (psychomotor), and elementary partial (focal motor). Each seizure type can be characterized by various symptoms. However, the seizures are generally not life threatening, lasting at most up to three minutes. The exception is status epilepticus, also called continuous seizure state. This is the occurrence of repetitive or continuous seizures and affects approximately 3 to 5% of those individuals suffering from epilepsy. It can exist with all types of seizures and may result in irreversible brain damage or death without prompt medical treatment.
Prior to the invention described in U.S. Pat. No. 5,523,742, parents of children afflicted with epilepsy, particularly status epilepticus, did not have a device for alerting the parents when the child may be having an epileptic seizure during sleeping hours. One recourse had been for the parents to sleep with the child, in the same bed, hoping to be awakened by the seizure during its early stages when the seizure motion may be quite mild. Often, the parents would choose to supplement this safeguard by using an alarm clock, set to sound every hour, to awaken and observe the state of the child. This, of course, places an extraordinary burden on both the child and the parents and is inherently unreliable as seizures may occur at any time. Moreover, the intermittent sleep afforded the parents as well as the desire for privacy by the child and by the parents make the procedure impractical and inefficient.
Continuous visual monitoring of the afflicted individual is usually impossible and periodic monitoring is often insufficient.
Monitors described in U.S. Pat. Nos. 5,523,742 and 5,610,590 provide relief during sleeping hours, but are inappropriate for reliably discriminating anomalous activity from the casual motion associated with normal quiet daytime activities. The use of either of these monitors would produce an unacceptably high false alarm rate resulting in undue anxiety and a loss of faith in the device.
One motion sensor that has found some applicability is disclosed in European Patent No. 87110092.1, filed Jul. 13, 1987. This device detects motion using a single moving object rolling on solid surfaces in which either the object or the surface, or both, have facets that interrupt the movement of the object on the surface. That sensor, of course, is intended to control the functioning of, heart pacemakers, which presents entirely different technical and medical problems to solve. For this reason, the European Patent is able to use microphones to sense the activity of the object, thus consuming considerable electric power.
Motion sensor devices are obvious solutions to the aforementioned problem, provided that such devices be designed to ignore the casual motions of a child (rolling over, etc.) while responding to those motions characteristic of a seizure, however mild at the beginning. Existing motion sensor devices such as accelerometers or displacement followers could conceivably be designed to detect certain types of motion while ignoring others, but are invariably expensive, consume excessive power, and, when the required signal conditioning equipment is included, form a bulky package. Moreover, these devices commonly require electrical connections between the transducer (affixed to the patient) and its associated equipment located near, but not on, the patient.
Accordingly, it is an object of this invention to provide a device for sensing a type of motion of concern while ignoring, for the most part, other non-harmful motion such as ordinary movement.
Another object of this invention is to provide a monitoring device for use during the day time as well as at night.
Still another object of this invention is to provide a monitoring device in which the user is able to attend class or do other activities without setting off unacceptably frequent false alarms.
Yet another object of this invention is to provide a simple, effective device for monitoring epileptics using a sensor that is easy to manufacture.
Other objects will appear hereinafter.